1. Field of the Invention
The invention relates to a sealing strip for sealing two machine parts. More specifically, the invention is a sealing strip having a separation element that effectively prevents two longitudinal sealing strips from coming into frictional contact and provides excellent sealing properties.
2. Description of the Related Art
German reference DE-U 19 55 711 discloses a radial piston seal for a rotary machine in which a filler body, under preloading, bears a sealing body. The filler body is divided in the transverse direction and is preloaded in the longitudinal direction by a spring element. The sealing bodies on both sides of the filler body must be fixedly connected to the filler body. Consequently, the internal stress of the sealing bodies counteracts the spring force of the spring element. The sealing bodies are of disk-like design and therefore cover a movement gap between the filler body parts.
One problem with this configuration is that the sealing bodies inevitably have a relatively large cross section and therefore a corresponding spring rate in the longitudinal or tension direction. Consequently, it is necessary to employ relatively high spring forces, but because of the space available these can only be achieved with difficulty. Once could envisage the sealing bodies being of annular design, in accordance with the principle described in DE 43 37 815 A1, but then there would be a leakage problem, since the movement gap between the filler pieces is not covered.
German reference DE 43 43 924 A1 describes a sealing arrangement for sealing two machine parts which move in translation relative to one another. The sealing arrangement comprises two sealing parts which, via a connecting web, form a single-piece unit, the connecting web being closed over its entire surface.
The object of the present invention is to develop a sealing strip which is preloaded in the longitudinal direction, in which the spring forces required are low and the leakage rate is minimized.
The separating element effectively prevents the two longitudinally displaceable sealing strips from coming into frictional contact or even a positive lock caused by deformation forces.
Briefly stated, the present invention is a sealing strip for sealing a space between two parts of a machine. The two parts form a groove for receiving the sealing strip. The groove has at least one wall along a longitudinal direction and a base. The sealing strip includes a filler piece, at least one spring element, at least one sealing body and a separating element. The filler piece has a top end and a bottom end and is divided into two filler piece parts along the longitudinal direction. The filler piece parts are capable of independent longitudinal displacement with respect to one another. The at least one spring element is arranged between the filler piece parts for preloading the filler piece into the groove. There is one sealing body for the top end and one sealing body for the bottom end of the filler piece. Each sealing body is formed in a frame-like shape for surrounding its respective end of the filler piece. The separating element is arranged between the filler piece parts for separating the filler piece parts and extends longitudinally from an end of the divided filler piece to at least a point where a sealing body surrounds the divided filler piece.
In a further embodiment of the present invention, the filler piece has at least one pocket-like cutout in which the at least one spring element is arranged. This prevents the possibility of a leak forming. Furthermore, contact between the groove side walls and the spring element, which could impair the function of the spring element, is prevented.
Advantageously, the preloading is exerted on the sealing body by a separate preloading element, the preloading element being guided at the sides by at least one web of the filler piece. As a result of the functions of xe2x80x9cgenerating the preloading forcexe2x80x9d and xe2x80x9csealingxe2x80x9d being separate, it is possible in each case to use optimized materials. The web section facilitates the fitting of the sealing strip as a whole, since the position of the preloading element inside the sealing strip is defined. In a further advantageous configuration, the web is designed as at least one web section, and furthermore the web section of the filler piece is formed on a single end-side end face. By means of the web on the end face, the compressive stress caused by the load exerted by the spring element on the sealing body is reduced, since the end face bears part of this force. Furthermore, the web section is restricted to one end-side end face. A greater degree of design freedom is obtained by dispensing with a web on all sides.
Furthermore, the sealing body has a transition surface between a sealing surface on the groove base side and a sealing surface on the groove wall side. In terms of production engineering, it is difficult to produce a sharp-edged transition in the region of contact between two groove surfaces. Therefore, the sealing body is also designed with a transition surface.
To prevent the sealing strip from being fitted the wrong way round, the transition surface is formed on both sides starting from the sealing surface on the groove base side.
The transition between the groove base and the groove side walls can only be produced within a limited manufacturing tolerance if acceptable outlay is to be maintained. To ensure that it is still not necessary to accept leakage in the region of the transition surface, a defined deformation area along a limited region of the length of the sealing surface is provided on the groove base side and on the groove wall side. Limiting the deformation area has the advantage that only a small volume has to be adapted to the shape of the groove and therefore the formation forces are kept at a low level.
In view of the different requirements imposed on the action of the force from the preloading element, the preloading element is of different cross-sectional sizes over its peripheral length.
For example, the preloading element is of an average cross-sectional size in the region which comes into contact with the top and bottom sides of the filler piece compared to the other regions of the preloading element.
Therefore, the preloading body has a larger cross section in the region of that end face of the filler piece which is not subjected to pressure from the spring force of the spring element, while in the region of that end face which is subjected to pressure it is of a smaller cross-sectional size, compared to the average cross-sectional size. This makes it possible, on the one hand, to provide sufficient volume to be able to compensate for temperature-related changes in length and, on the other hand, to produce a sealing body of optimum size. It is desirable for the filler piece to have a coefficient of expansion similar to that of the sealing body.
In a further embodiment, the separating element is of elastic design in its plane which is perpendicular to the direction of force from the at least one spring element. For this purpose, the separating element has at least one transverse opening.
In view of the design of the sealing body, the separating element, over a length region, is of a greater height than the groove which is to be sealed. The aim is to avoid a leak occurring in the groove formed by the adjacent transition surfaces of the sealing bodies.
To minimize the compressive stresses in the separating element, the length region which is of the greater height is arranged in the region of the cutout.
A further measure for preventing a leak between the sealing bodies consists in the length region, of the separating element, which is of the greater height and the defined deformation area of the sealing body having an overlap in the longitudinal direction of the sealing strip. The intention is to prevent the deformation areas provided on the sealing bodies and on the separating element from forming a labyrinth while nevertheless allowing medium to flow around them.
To ensure that there is no need to take into account positional orientation about the transverse axis when fitting the separating element, the length region which is of the greater height is formed over substantially half the length of the separating element.
The invention is to be described in more detail with reference to the following description of the figures, in which:
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of the disclosure. For a better understanding of the invention, its operating advantages, and specific objects attained by its use, reference should be had to the drawing and descriptive matter in which there are illustrated and described preferred embodiments of the invention.